I have no idea why nobody hasn't done it before, so I did.
https://bitcointalk.org/index.php?topic=464885.0It's a dream come true for SHA-256D coins because you can design without care for difficulty retargets.
SHA-256D ASICs are only getting more popular. The coins they mine should be up to the latest in technology.
If you don't believe me, check the AmKoin block chain. KGW lookbehind is set for 1 hour on a 7m block time.
Throw 10Th/s on the network and the coin will normalize in 120 minutes. Yank it off and it will normalize again in another 120. Over that time, still an average 7m block time.
For coins designed with shorter block times ... you get the picture.
Check out the GitHub codebase. I included a few extra lines that look like sloppy coding, but will assist other SHA-256D developers to integrate KGW into their coins.